diff --git a/src/cmd/go/internal/list/list.go b/src/cmd/go/internal/list/list.go
index d8c75776bb..7965a84f99 100644
--- a/src/cmd/go/internal/list/list.go
+++ b/src/cmd/go/internal/list/list.go
@@ -381,12 +381,20 @@ func runList(cmd *base.Command, args []string) {
 			base.Fatalf("go list -test cannot be used with -m")
 		}
 
+		buildModIsDefault := (cfg.BuildMod == "")
 		if modload.Init(); !modload.Enabled() {
 			base.Fatalf("go list -m: not using modules")
 		}
+
+		modload.InitMod() // Parses go.mod and sets cfg.BuildMod.
 		if cfg.BuildMod == "vendor" {
-			base.Fatalf("go list -m: can't list modules with -mod=vendor\n\tuse -mod=mod or -mod=readonly to ignore the vendor directory")
+			if buildModIsDefault {
+				base.Fatalf("go list -m: can't list modules using the vendor directory\n\tUse -mod=mod or -mod=readonly to ignore it.")
+			} else {
+				base.Fatalf("go list -m: can't list modules with -mod=vendor\n\tUse -mod=mod or -mod=readonly to ignore the vendor directory.")
+			}
 		}
+
 		modload.LoadBuildList()
 
 		mods := modload.ListModules(args, *listU, *listVersions)
diff --git a/src/cmd/go/internal/modload/init.go b/src/cmd/go/internal/modload/init.go
index cda6c93652..2f15093158 100644
--- a/src/cmd/go/internal/modload/init.go
+++ b/src/cmd/go/internal/modload/init.go
@@ -290,6 +290,9 @@ func die() {
 
 // InitMod sets Target and, if there is a main module, parses the initial build
 // list from its go.mod file, creating and populating that file if needed.
+//
+// As a side-effect, InitMod sets a default for cfg.BuildMod if it does not
+// already have an explicit value.
 func InitMod() {
 	if len(buildList) > 0 {
 		return
diff --git a/src/cmd/go/testdata/script/mod_convert_vendor_json.txt b/src/cmd/go/testdata/script/mod_convert_vendor_json.txt
index 47d111d4c1..2f5ccec32c 100644
--- a/src/cmd/go/testdata/script/mod_convert_vendor_json.txt
+++ b/src/cmd/go/testdata/script/mod_convert_vendor_json.txt
@@ -10,7 +10,7 @@ stderr '\s*cd \.\. && go mod init'
 # The command we suggested should succeed.
 cd ..
 go mod init
-go list -m all
+go list -mod=mod -m all
 stdout '^m$'
 
 -- $WORK/test/vendor/vendor.json --
diff --git a/src/cmd/go/testdata/script/mod_convert_vendor_manifest.txt b/src/cmd/go/testdata/script/mod_convert_vendor_manifest.txt
index 68edb9dc29..6f3a145430 100644
--- a/src/cmd/go/testdata/script/mod_convert_vendor_manifest.txt
+++ b/src/cmd/go/testdata/script/mod_convert_vendor_manifest.txt
@@ -10,7 +10,7 @@ stderr '\s*cd \.\. && go mod init'
 # The command we suggested should succeed.
 cd ..
 go mod init
-go list -m all
+go list -mod=mod -m all
 stdout '^m$'
 
 -- $WORK/test/vendor/manifest --
diff --git a/src/cmd/go/testdata/script/mod_getmode_vendor.txt b/src/cmd/go/testdata/script/mod_getmode_vendor.txt
index 21fec5b85f..baa79a083a 100644
--- a/src/cmd/go/testdata/script/mod_getmode_vendor.txt
+++ b/src/cmd/go/testdata/script/mod_getmode_vendor.txt
@@ -11,7 +11,7 @@ stdout '^rsc.io/quote v1.5.1 .*vendor[\\/]rsc.io[\\/]quote$'
 stdout '^golang.org/x/text v0.0.0.* .*vendor[\\/]golang.org[\\/]x[\\/]text[\\/]language$'
 
 ! go list -mod=vendor -m rsc.io/quote@latest
-stderr 'go list -m: can''t list modules with -mod=vendor\n\tuse -mod=mod or -mod=readonly to ignore the vendor directory'
+stderr 'go list -m: can''t list modules with -mod=vendor\n\tUse -mod=mod or -mod=readonly to ignore the vendor directory.'
 ! go get -mod=vendor -u
 stderr 'flag provided but not defined: -mod'
 
diff --git a/src/cmd/go/testdata/script/mod_vendor.txt b/src/cmd/go/testdata/script/mod_vendor.txt
index 9b716906e5..17fb2f3c16 100644
--- a/src/cmd/go/testdata/script/mod_vendor.txt
+++ b/src/cmd/go/testdata/script/mod_vendor.txt
@@ -35,7 +35,7 @@ stdout 'src[\\/]vendor[\\/]x'
 # 'go list -mod=vendor -m' does not have enough information to list modules
 # accurately, and should fail.
 ! go list -mod=vendor -f {{.Dir}} -m x
-stderr 'can''t list modules with -mod=vendor\n\tuse -mod=mod or -mod=readonly to ignore the vendor directory'
+stderr 'can''t list modules with -mod=vendor\n\tUse -mod=mod or -mod=readonly to ignore the vendor directory.'
 
 # 'go list -mod=mod' should report packages outside the import graph,
 # but 'go list -mod=vendor' should error out for them.
diff --git a/src/cmd/go/testdata/script/mod_vendor_auto.txt b/src/cmd/go/testdata/script/mod_vendor_auto.txt
index 7abe833f57..6e79f6b994 100644
--- a/src/cmd/go/testdata/script/mod_vendor_auto.txt
+++ b/src/cmd/go/testdata/script/mod_vendor_auto.txt
@@ -17,10 +17,10 @@ stdout '^'$WORK'[/\\]auto[/\\]vendor[/\\]example.com[/\\]printversion$'
 stdout '^'$WORK'[/\\]auto[/\\]vendor[/\\]example.com[/\\]version$'
 
 ! go list -m all
-stderr 'can''t list modules with -mod=vendor'
+stderr 'can''t list modules with -mod=vendor\n\tUse -mod=mod or -mod=readonly to ignore the vendor directory.'
 
 ! go list -m -f '{{.Dir}}' all
-stderr 'can''t list modules with -mod=vendor'
+stderr 'can''t list modules with -mod=vendor\n\tUse -mod=mod or -mod=readonly to ignore the vendor directory.'
 
 # An explicit -mod=mod should force the vendor directory to be ignored.
 env GOFLAGS=-mod=mod
@@ -103,6 +103,15 @@ stdout '^'$WORK'[/\\]auto$'
 stdout '^'$WORK'[/\\]auto[/\\]vendor[/\\]example.com[/\\]printversion$'
 stdout '^'$WORK'[/\\]auto[/\\]vendor[/\\]example.com[/\\]version$'
 
+# ...but 'go list -m' should continue to fail, this time without
+# referring to a -mod default that the user didn't set.
+! go list -m all
+stderr 'can''t list modules using the vendor directory\n\tUse -mod=mod or -mod=readonly to ignore it.'
+
+! go list -m -f '{{.Dir}}' all
+stderr 'can''t list modules using the vendor directory\n\tUse -mod=mod or -mod=readonly to ignore it.'
+
+
 # 'go mod init' should work if there is already a GOPATH-mode vendor directory
 # present. If there are no module dependencies, -mod=vendor should be used by
 # default and should not fail the consistency check even though no module